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Re: st: Changing range in sts graph


From   "Svend Juul" <SJ@SOCI.AU.DK>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Changing range in sts graph
Date   Fri, 7 Dec 2007 10:08:49 +0100

Diego Bellavia <messadua@yahoo.it> wrote:

> I have a Kaplan Meyer curve I built with sts command. 
> The curve is nice but I would like to reduce the range of time showed
> to highlight the first part of the graph (where I have more events).
> I tried with the xscale (range (0 100)) option but without success. 

Maarten suggested:

   sysuse cancer, clear
   stset studytim,failure(died)
   sts graph 
   sts graph if _t < 20

and Allen Buxton suggested:

   local rangelimit=100
   replace _d=0  if _t>`rangelimit'
   replace _t=`rangelimit' if _t>`rangelimit'

Nick got nervous:

Doesn't any messing with _t mess up anything later with the same 
survival dataset? Sounds a bad idea to me. See Maarten's solution. 

-----------------------------------------------------

Allen's suggestion is right, Maarten's is wrong. It is easy to
see with -sts list- :

   sysuse cancer, clear
   stset studytim,failure(died)
   sts list 

   // Maarten's suggestion:
   sts list if  _t < 20    

   // Allen's suggestion (simplified):
   replace _d=0  if _t>20
   replace _t=min(_t,20)
   sts list

In Maartens suggestion, persons surviving 20 months or more
were excluded from the analysis, leading to a far too pessimistic
survival estimate at 19 months. In Allen's suggestion they
are correctly censored at 20 months.

Svend



__________________________________________

Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000  Aarhus C, Denmark
Phone: +45 8942 6090
Home:  +45 8693 7796
Email: sj@soci.au.dk
__________________________________________ 

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